Waveguide Diffusers for LIDARs

ABSTRACT

One example system comprises a light source configured to emit light. The system also comprises a waveguide configured to guide the emitted light from a first end of the waveguide toward a second end of the waveguide. The waveguide has an output surface between the first end and the second end. The system also comprises a plurality of mirrors including a first mirror and a second mirror. The first mirror reflects a first portion of the light toward the output surface. The second mirror reflects a second portion of the light toward the output surface. The first portion propagates out of the output surface toward a scene as a first transmitted light beam. The second portion propagates out of the output surface toward the scene as a second transmitted light beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/982,078, filed Nov. 7, 2022, which is a continuation of U.S. patentapplication Ser. No. 16/140,535, filed Sep. 25, 2018. The foregoingapplications are incorporated herein by reference.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Light detectors, such as photodiodes, single photon avalanche diodes(SPADs), or other types of avalanche photodiodes (APDs), can be used todetect light that is imparted on their surfaces (e.g., by outputting anelectrical signal, such as a voltage or a current, that indicates anintensity of the light). Many types of such devices are fabricated outof semiconducting materials, such as silicon. In order to detect lightover a large geometric area, multiple light detectors can be arranged asan array. These arrays are sometimes referred to as siliconphotomultipliers (SiPMs) or multi-pixel photon counters (MPPCs).

Light detectors can be employed in a variety of systems, such ascameras, scanners, imagers, and motion sensors, among other examples.Some active sensing systems, such as light detection and ranging (LIDAR)systems, 3D scanners, computing tomography (CT) scanners, laserscanners, and infrared (IR) scanners, among other examples, may operateby emitting light and then detecting reflections (or other scatteredportions) of the emitted light. For example, a LIDAR system candetermine distances to environmental features while scanning through ascene to assemble a “point cloud” indicative of reflective surfaces inthe environment. Individual points in the point cloud can be determined,for example, by transmitting a laser pulse and detecting a returningpulse, if any, reflected from an object in the environment, and thendetermining a distance to the object according to a time delay betweenthe transmission of the pulse and the reception of the reflected pulse.

SUMMARY

In one example, a system comprises a light source configured to emitlight. The system also comprises a waveguide configured to guide thelight from a first end of the waveguide toward a second side of thewaveguide. The waveguide has an output surface between the first end andthe second end. The system also comprises a plurality of mirrorsincluding a first mirror and a second mirror. The first mirror reflectsa first portion of the light toward the output surface of the waveguide.The second mirror reflects a second portion of the light toward theoutput surface. The first portion propagates, after being reflected bythe first mirror, out of the output surface toward a scene as a firsttransmitted light beam. The second portion propagates, after beingreflected by the second mirror, out of the output surface toward thescene as a second transmitted light beam.

In another example, a light detection and ranging (LIDAR) devicecomprises a plurality of mirrors including a first mirror and a secondmirror. The LIDAR device transmits a plurality of light beams toilluminate a scene. The plurality of transmitted light beams includes afirst transmitted light beam and a second transmitted light beam. Theplurality of transmitted light beams is arranged spatially based on aphysical arrangement of the plurality of mirrors. The LIDAR device alsocomprises a light emitter and a waveguide. The waveguide is configuredto guide emitted light from the light emitter toward the plurality ofmirrors. The first mirror is configured to reflect a first portion ofthe light toward an output side of the waveguide as the firsttransmitted light beam. The second mirror reflects a second portion ofthe light toward the output side of the waveguide as the secondtransmitted light beam.

In yet another example, a method involves emitting light toward a firstend of a waveguide. The method also involves guiding, inside awaveguide, the light toward a second end of the waveguide. The waveguidehas an output surface between the first end and the second end. Themethod also involves reflecting a first portion of the light toward theoutput surface of the waveguide. The first portion propagates out of theoutput surface of the waveguide toward a scene as a first transmittedlight beam. The method also involves reflecting a second portion of thelight toward the output surface of the waveguide. The second portionpropagates out of the output surface of the waveguide toward the sceneas a second transmitted light beam.

In still another example, a system comprises means for emitting lighttoward a first end of a waveguide. The system also comprises means forguiding, inside a waveguide, the emitted light toward a second end ofthe waveguide. The waveguide has an output surface between the first endand the second end. The system also comprises means for reflecting afirst portion of the guided light toward the output surface of thewaveguide. The reflected first portion propagates out of the outputsurface of the waveguide toward a scene as a first transmitted lightbeam. The system also comprises means for reflecting a second portion ofthe guided light toward the output surface of the waveguide. Thereflected second portion propagates out of the output surface of thewaveguide toward the scene as a second transmitted light beam.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is an illustration of a system that includes an aperture,according to example embodiments.

FIG. 1B is another illustration of the system of FIG. 1A.

FIG. 2A is a simplified block diagram of a LIDAR device, according toexample embodiments.

FIG. 2B illustrates a perspective view of the LIDAR device of FIG. 2A.

FIG. 3A is an illustration of a system that includes a waveguide,according to example embodiments.

FIG. 3B illustrates a cross-section view of the system of FIG. 3A.

FIG. 4A illustrates a first cross-section view of a system that includesmultiple waveguides, according to example embodiments.

FIG. 4B illustrates a second cross-section view of the system of FIG.4A.

FIG. 4C illustrates a third cross-section view of the system of FIG. 4A.

FIG. 4D illustrates a fourth cross-section view of the system of FIG.4A.

FIG. 5 is a flowchart of a method, according to example embodiments.

DETAILED DESCRIPTION

Any example embodiment or feature described herein is not necessarily tobe construed as preferred or advantageous over other embodiments orfeatures. The example embodiments described herein are not meant to belimiting. It will be readily understood that certain aspects of thedisclosed implementations can be arranged and combined in a wide varietyof different configurations. Furthermore, the particular arrangementsshown in the figures should not be viewed as limiting. It should beunderstood that other implementations might include more or less of eachelement shown in a given figure. In addition, some of the illustratedelements may be combined or omitted. Similarly, an exampleimplementation may include elements that are not illustrated in thefigures.

I. Overview

One example system includes a lens. The lens may be used to focus lightfrom a scene. However, the lens may also focus background light notintended to be observed by the system (e.g., sunlight). In order toselectively filter the light (e.g., separate background light from lightcorresponding to information within the scene), an opaque material(e.g., selectively etched metal, a glass substrate partially covered bya mask, etc.) may be placed behind the lens. The opaque material couldbe shaped as a slab, a sheet, or various other shapes in a variety ofembodiments. Within the opaque material, an aperture may be defined.With this arrangement, a portion of, or the entirety of, the lightfocused by the lens could be selected for transmission through theaperture.

In the direction of propagation of the light transmitted through theaperture, the system may include at least one light detector (e.g.,array of SPADs, etc.) arranged to detect at least a portion of thefocused light transmitted through the aperture.

The system may also include a light source that emits light, and awaveguide that receives the emitted light at an input end of thewaveguide. The waveguide guides the emitted light from the input end toan output end of the waveguide opposite the input end. The waveguide hasa given side that extends from the input end to the output end. At ornear the output end, the waveguide transmits at least a portion of theemitted light out of the given side and toward the lens. In general, theoutput end may be aligned with a path of the focused light propagatingfrom the lens to the light detector. In one embodiment, the emittedlight transmitted out of the waveguide may propagate through the sameaperture through which the focused light from the lens is transmittedtoward the light detector.

To facilitate transmitting the guided light out of the waveguide (andthrough the given side), in some examples, the system may include anoutput mirror disposed along a propagation path of the guided lightpropagating inside the waveguide (e.g., at or near the output end). Theoutput mirror may be tilted toward the given side of the waveguide. Assuch, the output mirror may reflect the guided light (or a portionthereof) toward a particular region of the given side. For example, theparticular region may be aligned with the path of the focused lighttransmitted through the aperture.

With this arrangement, the system may direct the emitted light in atransmit path that extends through the aperture and the lens (toward thescene); and the system may focus returning reflections of the emittedlight in a receive path that extends through the same lens and the sameaperture. Thus, in this example, the transmit and receive paths may bespatially co-aligned (e.g., because both paths are defined using thesame aperture and the same lens).

By spatially aligning the transmit path with the receive path, theexample system may reduce (or prevent) optical scanning distortionsassociated with parallax. For instance, if the transmit and receivepaths were instead spatially offset relative to one another (e.g.,mismatch between the respective pointing or viewing directions, etc.), ascanned representation of the scene could be affected by opticaldistortions such as parallax.

Other aspects, features, implementations, configurations, arrangements,and advantages are possible.

II. Example Systems and Devices

FIG. 1A is an illustration of a system 100 that includes an aperture,according to example embodiments. As shown, system 100 includes an array110 of light detectors (exemplified by detectors 112 and 114), anaperture 120 a defined within an opaque material 120, and a lens 130.System 100 may measure light 102 reflected or scattered by an object 198within a scene. In some instances, light 102 may also include lightpropagating directly from background sources (not shown) toward lens130. In some examples, system 100 may be included in a light detectionand ranging (LIDAR) device. In one example, the LIDAR device may be usedfor navigation of an autonomous vehicle. In some embodiments, system100, or portions thereof, may be contained within an area that isunexposed to external light other than through lens 130. This may reducean amount of ambient light (which may affect measurements) reaching thedetectors in array 110.

Array 110 includes an arrangement of light detectors, exemplified bydetectors 112 and 114. In various embodiments, array 110 may havedifferent shapes. As shown, array 110 has a rectangular shape. However,in other embodiments, array 110 may be circular or may have a differentshape. The size of array 110 may be selected according to an expectedcross-sectional area of light 110 diverging from aperture 120 a. Forexample, the size of array 110 may be based on the distance betweenarray 110 and aperture 120 a, the distance between aperture 120 a andlens 130, dimensions of aperture 120 a, optical characteristics of lens130, among other factors. In some embodiments, array 110 may be movable.For example, the location of array 110 may be adjustable so as to becloser to, or further from, aperture 120 a. To that end, for instance,array 110 could be mounted on an electrical stage capable of translatingin one, two, or three dimensions.

Further, in some implementations, array 110 may provide one or moreoutputs to a computing device or logic circuitry. For example, amicroprocessor-equipped computing device may receive electrical signalsfrom array 110 which indicate an intensity of light 102 incident onarray 110. The computing device may then use the electrical signals todetermine information about object 198 (e.g., distance between object198 and system 100, etc.). In some embodiments, some or all of the lightdetectors within array 110 may be interconnected with one another inparallel. To that end, for example, array 110 may be a SiPM or an MPPC,depending on the particular arrangement and type of the light detectorswithin array 110. By connecting the light detectors in a parallelcircuit configuration, for instance, the outputs from the lightdetectors can be combined to effectively increase a detection area inwhich a photon in light 102 can be detected (e.g., shaded region ofarray 110 shown in FIG. 1A).

Light detectors 112, 114, etc., may include various types of lightdetectors. In one example, detectors 112, 114, etc., include SPADs.SPADs may employ avalanche breakdown within a reverse biased p-njunction (i.e., diode) to increase an output current for a givenincident illumination on the SPAD. Further, SPADs may be able togenerate multiple electron-hole pairs for a single incident photon. Inanother example, light detectors 112, 114, etc., may include linear-modeavalanche photodiodes (APDs). In some instances, APDs or SPADs may bebiased above an avalanche breakdown voltage. Such a biasing conditionmay create a positive feedback loop having a loop gain that is greaterthan one. Further, SPADs biased above the threshold avalanche breakdownvoltage may be single photon sensitive. In other examples, lightdetectors 112, 114, etc., may include photoresistors, charge-coupleddevices (CCDs), photovoltaic cells, and/or any other type of lightdetector.

In some implementations, array 110 may include more than one type oflight detector across the array. For example, array 110 can beconfigured to detect multiple predefined wavelengths of light 102. Tothat end, for instance, array 110 may comprise some SPADs that aresensitive to one range of wavelengths and other SPADs that are sensitiveto a different range of wavelengths. In some embodiments, lightdetectors 110 may be sensitive to wavelengths between 400 nm and 1.6 μm(visible and/or infrared wavelengths). Further, light detectors 110 mayhave various sizes and shapes within a given embodiment or acrossvarious embodiments. In some embodiments, light detectors 112, 114,etc., may include SPADs that have package sizes that are 1%, 0.1%, or0.01% of the area of array 110.

Opaque material 120 (e.g., mask, etc.) may block a portion of light 102from the scene (e.g., background light) that is focused by the lens 130from being transmitted to array 110. For example, opaque material 120may be configured to block certain background light that could adverselyaffect the accuracy of a measurement performed by array 110.Alternatively or additionally, opaque material 120 may block light inthe wavelength range detectable by detectors 112, 114, etc. In oneexample, opaque material 120 may block transmission by absorbing aportion of incident light. In another example, opaque material 120 mayblock transmission by reflecting a portion of incident light. Anon-exhaustive list of example implementations of opaque material 120includes an etched metal, a polymer substrate, a biaxially-orientedpolyethylene terephthalate (BoPET) sheet, or a glass overlaid with anopaque mask, among other possibilities. In some examples, opaquematerial 120, and therefore aperture 120 a, may be positioned at or neara focal plane of lens 130.

Aperture 120 a provides a port within opaque material 120 through whichlight 102 (or a portion thereof) may be transmitted. Aperture 120 a maybe defined within opaque material 120 in a variety of ways. In oneexample, opaque material 120 (e.g., metal, etc.) may be etched to defineaperture 120 a. In another example, opaque material 120 may beconfigured as a glass substrate overlaid with a mask, and the mask mayinclude a gap that defines aperture 120 a (e.g., via photolithography,etc.). In various embodiments, aperture 120 a may be partially or whollytransparent, at least to wavelengths of light that are detectable bylight detectors 112, 114, etc. For example, where opaque material 120 isa glass substrate overlaid with a mask, aperture 120 a may be defined asa portion of the glass substrate not covered by the mask, such thataperture 120 a is not completely hollow but rather made of glass. Thus,in some instances, aperture 120 a may be nearly, but not entirely,transparent to one or more wavelengths of light 102 (e.g., glasssubstrates are typically not 100% transparent). Alternatively, in someinstances, aperture 120 a may be formed as a hollow region of opaquematerial 120.

In some examples, aperture 120 a (in conjunction with opaque material120) may be configured to spatially filter light 102 from the scene atthe focal plane. To that end, for example, light 102 may be focused ontoa focal plane along a surface of opaque material 120, and aperture 120 amay allow only a portion of the focused light to be transmitted to array110. As such, aperture 120 a may behave as an optical pinhole. In oneembodiment, aperture 120 a may have a cross-sectional area of between0.02 mm² and 0.06 mm² (e.g., 0.04 mm²). In other embodiments, aperture120 a may have a different cross-sectional area depending on variousfactors such as optical characteristics of lens 130, distance to array110, noise rejection characteristics of the light detectors in array110, etc.

Thus, although the term “aperture” as used above with respect toaperture 120 a may describe a recess or hole in an opaque materialthrough which light may be transmitted, it is noted that the term“aperture” may include a broad array of optical features. In oneexample, as used throughout the description and claims, the term“aperture” may additionally encompass transparent or translucentstructures defined within an opaque material through which light can beat least partially transmitted. In another example, the term “aperture”may describe a structure that otherwise selectively limits the passageof light (e.g., through reflection or refraction), such as a mirrorsurrounded by an opaque material. In one example embodiment, mirrorarrays surrounded by an opaque material may be arranged to reflect lightin a certain direction, thereby defining a reflective portion, which maybe referred to as an “aperture”.

Although aperture 120 a is shown to have a rectangular shape, it isnoted that aperture 120 a can have a different shape, such as a roundshape, circular shape, elliptical shape, among others. In some examples,aperture 120 a can alternatively have an irregular shape specificallydesigned to account for optical aberrations within system 100. Forexample, a keyhole shaped aperture may assist in accounting for parallaxoccurring between an emitter (e.g., light source that emits light 102)and a receiver (e.g., lens 130 and array 110). The parallax may occur ifthe emitter and the receiver are not located at the same position, forexample. Other irregular aperture shapes are also possible, such asspecifically shaped apertures that correspond with particular objectsexpected to be within a particular scene or irregular apertures thatselect specific polarizations of light 102 (e.g., horizontal or verticalpolarizations).

Lens 130 may focus light 102 from the scene onto the focal plane whereaperture 120 a is positioned. With this arrangement, the light intensitycollected from the scene, at lens 130, may be focused to have a reducedcross-sectional area over which light 102 is projected (i.e., increasingthe spatial power density of light 102). For example, lens 130 mayinclude a converging lens, a biconvex lens, and/or a spherical lens,among other examples. Alternatively, lens 130 can be implemented as aconsecutive set of lenses positioned one after another (e.g., a biconvexlens that focuses light in a first direction and an additional biconvexlens that focuses light in a second direction). Other types of lensesand/or lens arrangements are also possible. In addition, system 100 mayinclude other optical elements (e.g., mirrors, etc.) positioned nearlens 130 to aid in focusing light 102 incident on lens 130 onto opaquematerial 120.

Object 198 may be any object positioned within a scene surroundingsystem 100. In implementations where system 100 is included in a LIDARdevice, object 198 may be illuminated by a LIDAR transmitter that emitslight (a portion of which may return as light 102). In exampleembodiments where the LIDAR device is used for navigation of anautonomous vehicle, object 198 may be or include pedestrians, othervehicles, obstacles (e.g., trees, debris, etc.), or road signs, amongother types of objects.

As noted above, light 102 may be reflected or scattered by object 198,focused by lens 130, transmitted through aperture 120 a in opaquematerial 120, and measured by light detectors in array 110. Thissequence may occur (e.g., in a LIDAR device) to determine informationabout object 198. In some embodiments, light 102 measured by array 110may additionally or alternatively include light reflected or scatteredoff multiple objects, transmitted by a transmitter of another LIDARdevice, ambient light, sunlight, among other possibilities.

In some examples, the wavelength(s) of light 102 used to analyze object198 may be selected based on the types of objects expected to be withina scene and their expected distance from lens 130. For example, if anobject expected to be within the scene absorbs all incoming light of 500nm wavelength, a wavelength other than 500 nm may be selected toilluminate object 198 and to be analyzed by system 100. The wavelengthof light 102 (e.g., if transmitted by a transmitter of a LIDAR device)may be associated with a source that generates light 102 (or a portionthereof). For example, if the light is generated by a laser diode, light102 may comprise light within a wavelength range that includes 900 nm(or other infrared and/or visible wavelength). Thus, various types oflight sources are possible for generating light 102 (e.g., an opticalfiber amplifier, various types of lasers, a broadband source with afilter, etc.).

As shown, light 102 diverges as it propagates away from aperture 120 a.Due to the divergence, a detection area at array 110 (e.g., shown asshaded area illuminated by light 102) may be larger than across-sectional area of aperture 120 a. An increased detection area(e.g., measured in m²) for a given light power (e.g., measured in W) maylead to a reduced light intensity (e.g., measured in

$\left. \frac{W}{m^{2}} \right)$

incident on array 110.

The reduction in light intensity may be particularly beneficial inembodiments where array 110 includes SPADs or other light detectorshaving high sensitivities. For example, SPADs derive their sensitivityfrom a large reverse-bias voltage that produces avalanche breakdownwithin a semiconductor. This avalanche breakdown can be triggered by theabsorption of a single photon, for example. Once a SPAD absorbs a singlephoton and the avalanche breakdown begins, the SPAD cannot detectadditional photons until the SPAD is quenched (e.g., by restoring thereverse-bias voltage). The time until the SPAD is quenched may bereferred to as the recovery time. If additional photons are arriving attime intervals approaching the recovery time (e.g., within a factor often), the SPAD may begin to saturate, and the measurements by the SPADmay thus become less reliable. By reducing the light power incident onany individual light detector (e.g., SPAD) within array 110, the lightdetectors (e.g., SPADs) in array 110 may remain unsaturated. As aresult, the light measurements by each individual SPAD may have anincreased accuracy.

FIG. 1B is another illustration of system 100. As shown, system 100 alsoincludes a light filter 132 and a light emitter 140. Filter 132 mayinclude any optical filter configured to selectively transmit lightwithin a predefined wavelength range. For example, filter 132 can beconfigured to selectively transmit light within a visible wavelengthrange, an infrared wavelength range, or any other wavelength range ofthe light signal emitted by emitter 140. For example, optical filter 132may be configured to attenuate light of particular wavelengths or divertlight of particular wavelengths away from the array 110. For instance,optical filter 132 may attenuate or divert wavelengths of light 102 thatare outside of the wavelength range emitted by emitter 140. Therefore,optical filter 132 may, at least partially, reduce ambient light orbackground light from adversely affecting measurements by array 110.

In various embodiments, optical filter 132 may be located in variouspositions relative to array 110. As shown, optical filter 132 is locatedbetween lens 130 and opaque material 120. However, optical filter 132may alternatively be located between lens 130 and object 198, betweenopaque material 120 and array 110, combined with array 110 (e.g., array110 may have a surface screen that optical filter 132, or each of thelight detectors in array 110 may individually be covered by a separateoptical filter, etc.), combined with aperture 120 a (e.g., aperture 120a may be transparent only to a particular wavelength range, etc.), orcombined with lens 130 (e.g., surface screen disposed on lens 130,material of lens 130 transparent only to a particular wavelength range,etc.), among other possibilities.

As shown in FIG. 1B, light emitter 140 emits a light signal to bemeasured by array 110. Emitter 140 may include a laser diode, fiberlaser, a light-emitting diode, a laser bar, a nanostack diode bar, afilament, a LIDAR transmitter, or any other light source. As shown,emitter 140 may emit light which is reflected by object 198 in the sceneand ultimately measured (at least a portion thereof) by array 110. Insome embodiments, emitter 140 may be implemented as a pulsed laser (asopposed to a continuous wave laser), allowing for increased peak powerwhile maintaining an equivalent continuous power output.

FIG. 2A is a simplified block diagram of a LIDAR device 200, accordingto example embodiments. In some example embodiments, LIDAR device 200can be mounted to a vehicle and employed to map a surroundingenvironment (e.g., the scene including object 298, etc.) of the vehicle.As shown, LIDAR device 200 includes a laser emitter 240 that may besimilar to emitter 140, a system 290 that may be similar to system 100,a controller 292, a rotating platform 294, and one or more actuators296.

System 290 includes an array 210 of light detectors, an opaque material220, and a lens 230, which can be similar, respectively, to array 110,opaque material 120, and lens 130. It is noted that LIDAR device 200 mayalternatively include more or fewer components than those shown. Forexample, LIDAR device 200 may include an optical filter (e.g., filter132). Thus, system 290 can be implemented similarly to system 100 and/orany other system herein.

Device 200 may operate emitter 240 to emit light 202 toward a scene thatincludes object 298, similarly to, respectively, emitter 140, light 102,and object 198 of device 100. To that end, in some implementations,emitter 240 (and/or one or more other components of device 200) can beconfigured as a LIDAR transmitter of LIDAR device 200. Device 200 maythen detect reflections of light 202 returning from the scene todetermine information about object 298. To that end, in someimplementations, array 210 (and/or one or more other components ofsystem 290) can be configured as a LIDAR receiver of LIDAR device 200.

Controller 292 may be configured to control one or more components ofLIDAR device 200 and to analyze signals received from the one or morecomponents. To that end, controller 292 may include one or moreprocessors (e.g., a microprocessor, etc.) that execute instructionsstored in a memory (not shown) of device 200 to operate device 200.Additionally or alternatively, controller 292 may include digital oranalog circuitry wired to perform one or more of the various functionsdescribed herein.

Rotating platform 294 may be configured to rotate about an axis toadjust a pointing direction of LIDAR 200 (e.g., direction of emittedlight 202 relative to the environment, etc.). To that end, rotatingplatform 294 can be formed from any solid material suitable forsupporting one or more components of LIDAR 200. For example, system 290(and/or emitter 240) may be supported (directly or indirectly) byrotating platform 294 such that each of these components moves relativeto the environment while remaining in a particular relative arrangementin response to rotation of rotating platform 294. In particular, themounted components could be rotated (simultaneously) about an axis sothat LIDAR 200 may adjust its pointing direction while scanning thesurrounding environment. In this manner, a pointing direction of LIDAR200 can be adjusted horizontally by actuating rotating platform 294 todifferent directions about the axis of rotation. In one example, LIDAR200 can be mounted on a vehicle, and rotating platform 294 can berotated to scan regions of the surrounding environment at variousdirections from the vehicle.

In order to rotate platform 294 in this manner, one or more actuators296 may actuate rotating platform 294. To that end, actuators 296 mayinclude motors, pneumatic actuators, hydraulic pistons, and/orpiezoelectric actuators, among other possibilities.

With this arrangement, controller 292 could operate actuator(s) 296 torotate rotating platform 294 in various ways so as to obtain informationabout the environment. In one example, rotating platform 294 could berotated in either direction about an axis. In another example, rotatingplatform 294 may carry out complete revolutions about the axis such thatLIDAR 200 scans a 360° field-of-view (FOV) of the environment. In yetanother example, rotating platform 294 can be rotated within aparticular range (e.g., by repeatedly rotating from a first angularposition about the axis to a second angular position and back to thefirst angular position, etc.) to scan a narrower FOV of the environment.Other examples are possible.

Moreover, rotating platform 294 could be rotated at various frequenciesso as to cause LIDAR 200 to scan the environment at various refreshrates. In one embodiment, LIDAR 200 may be configured to have a refreshrate of 10 Hz. For example, where LIDAR 200 is configured to scan a 360°FOV, actuator(s) 296 may rotate platform 294 for ten complete rotationsper second.

FIG. 2B illustrates a perspective view of LIDAR device 200. As shown,device 200 also includes a transmitter lens 231 that directs emittedlight from emitter 240 toward the environment of device 200. To thatend, FIG. 2B illustrates an example implementation of device 200 whereemitter 240 and system 290 each have separate respective optical lenses231 and 230. However, in other embodiments, device 200 can bealternatively configured to have a single shared lens for both emitter240 and system 290. By using a shared lens to both direct the emittedlight and receive the incident light (e.g., light 202), advantages withrespect to size, cost, and/or complexity can be provided. For example,with a shared lens arrangement, device 200 can reduce and/or preventparallax associated with transmitting light 202 (by emitter 240) from adifferent viewpoint than a viewpoint from which light 202 is received(by system 290).

As shown in FIG. 2B, light beams emitted by emitter 240 propagate fromlens 231 toward an environment of LIDAR 200, and then return (e.g.,after reflecting off one or more objects in the environment) asreflected light 202. LIDAR 200 may then receive reflected light 202(e.g., through lens 230) and provide data pertaining to the one or moreobjects (e.g., distance between the one or more objects and the LIDAR200, etc.).

Further, as shown in FIG. 2B, rotating platform 294 mounts system 290and emitter 240 in the particular relative arrangement shown. By way ofexample, if rotating platform 294 rotates about axis 201, the pointingdirections of system 290 and emitter 240 may simultaneously changeaccording to the particular relative arrangement shown. Through thisprocess, LIDAR 200 can scan different regions of the surroundingenvironment according to different rotational positions of LIDAR 200about axis 201. For instance, device 200 (and/or another computingsystem) can determine a three-dimensional map of a 360° (or less) viewof the environment of device 200 by processing data associated withdifferent pointing directions of LIDAR 200 as the LIDAR rotates aboutaxis 201.

In some examples, axis 201 may be substantially vertical. In theseexamples, the pointing direction of device 200 can be adjustedhorizontally by rotating system 290 (and emitter 240) about axis 201.

In some examples, system 290 (and emitter 240) can be tilted (relativeto axis 201) to adjust the vertical extents of the FOV of LIDAR 200. Byway of example, LIDAR device 200 can be mounted on top of a vehicle. Inthis example, system 290 (and emitter 240) can be tilted (e.g., towardthe vehicle) to collect more data points from regions of the environmentthat are closer to a driving surface on which the vehicle is locatedthan data points from regions of the environment that are above thevehicle. Other mounting positions, tilting configurations, and/orapplications of LIDAR device 200 are possible as well (e.g., on adifferent side of the vehicle, on a robotic device, or on any othermounting surface).

It is noted that the shapes, positions, and sizes of the variouscomponents of device 200 can vary, and are illustrated as shown in FIG.2B only for the sake of example.

Returning now to FIG. 2A, in some implementations, controller 292 mayuse timing information associated with a signal measured by array 210 todetermine a location (e.g., distance from LIDAR device 200) of object298. For example, in embodiments where emitter 240 is a pulsed laser,controller 292 can monitor timings of output light pulses and comparethose timings with timings of signal pulses measured by array 210. Forinstance, controller 292 can estimate a distance between device 200 andobject 298 based on the speed of light and the time of travel of thelight pulse (which can be calculated by comparing the timings). In oneimplementation, during the rotation of platform 294, emitter 240 mayemit light pulses (e.g., light 202), and system 290 may detectreflections of the emitted light pulses. Device 200 (or another computersystem that processes data from device 200) can then generate athree-dimensional (3D) representation of the scanned environment basedon a comparison of one or more characteristics (e.g., timing, pulselength, light intensity, etc.) of the emitted light pulses and thedetected reflections thereof.

In some implementations, controller 292 may be configured to account forparallax (e.g., due to laser emitter 240 and lens 230 not being locatedat the same location in space). By accounting for the parallax,controller 292 can improve accuracy of the comparison between the timingof the output light pulses and the timing of the signal pulses measuredby the array 210.

In some implementations, controller 292 could modulate light 202 emittedby emitter 240. For example, controller 292 could change the projection(e.g., pointing) direction of emitter 240 (e.g., by actuating amechanical stage, such as platform 294 for instance, that mounts emitter240). As another example, controller 292 could modulate the timing, thepower, or the wavelength of light 202 emitted by emitter 240. In someimplementations, controller 292 may also control other operationalaspects of device 200, such as adding or removing filters (e.g., filter132) along a path of propagation of light 202, adjusting relativepositions of various components of device 200 (e.g., array 210, opaquematerial 220 (and an aperture therein), lens 230, etc.), among otherpossibilities.

In some implementations, controller 292 could also adjust an aperture(not shown) within material 220. In some embodiments, the aperture maybe selectable from a number of apertures defined within the opaquematerial. In some embodiments, a MEMS mirror could be located betweenlens 230 and opaque material 220 and may be adjustable by controller 292to direct the focused light from lens 230 to one of the multipleapertures. In some embodiments, the various apertures may have differentshapes and/or sizes. In some embodiments, an aperture may be defined byan iris (or other type of diaphragm). The iris may be expanded orcontracted by controller 292, for example, to control the size or shapeof the aperture.

Thus, in some examples, LIDAR device 200 can modify a configuration ofsystem 290 to obtain additional or different information about object298 and/or the scene. In one example, controller 292 may select a largeraperture in response to a determination that background noise receivedby system 290 from the scene is currently relatively low (e.g., duringnight-time). The larger aperture, for instance, may allow system 290 todetect a portion of light 202 that would otherwise be focused by lens230 outside the aperture. In another example, controller 292 may selecta different aperture position to intercept a portion of light 202arriving at lens 230 from a particular receive path or viewing angle. Inyet another example, controller 292 could adjust the distance between anaperture and light detector array 210. By doing so, for instance, thecross-sectional area of a detection region in array 210 (i.e.,cross-sectional area of light 202 at array 210) can be adjusted as well.For example, in FIG. 1A, the detection region of array 110 is indicatedby shading on array 110.

However, in some scenarios, the extent to which the configuration ofsystem 290 can be modified may depend on various factors such as a sizeof LIDAR device 200 or system 290, among other factors. For example,referring back to FIG. 1A, a size of array 110 may depend on an extentof divergence of light 102 from a location of aperture 120 a to alocation of array 110. Thus, for instance, the maximum vertical andhorizontal extents of array 110 may depend on the physical spaceavailable for accommodating system 100 within a LIDAR device. Similarly,for instance, an available range of values for the distance betweenarray 110 and aperture 120 a may also be limited by physical limitationsof a LIDAR device where system 100 is employed. Accordingly, exampleimplementations are described herein for space-efficient systems thatprovide an increased detection area in which light detectors canintercept light from the scene and reduce background noise.

In some scenarios, a scanned representation of object 298 (e.g.,computed using controller 292, or using an external computer thatreceives data from LIDAR 200, etc.) may be susceptible to parallaxassociated with a spatial offset between the transmit path of light 202(e.g., emitted by emitter 240 via lens 231 of FIG. 2B) and the receivepath of reflected light 202 incident on lens 230. Accordingly, exampleimplementations are described herein for reducing and/or mitigating theeffects of such parallax. In one example, device 200 may alternativelyincorporate emitter 240 within system 290 to co-align the LIDAR transmitand receive paths of LIDAR 200 (e.g., by causing both paths to extendthrough the same lens 230 and a same aperture in opaque material 220).

It is noted that the various functional blocks shown for the componentsof device 200 can be redistributed, rearranged, combined, and/orseparated in various ways different than the arrangement shown.

FIG. 3A is an illustration of a system 300 that includes a waveguide350, according to example embodiments. In some implementations, system300 can be included in device 200 instead of or in addition totransmitter 240 and system 290. As shown, system 300 may measure light302 reflected by an object 398 within a scene similarly to,respectively, system 100, light 102, and object 198. Further, as shown,system 300 includes a light detector array 310, an opaque material 320,an aperture 320 a, a lens 330, and a light source 340, which may besimilar, respectively, to array 110, material 120, aperture 120 a, lens130, and emitter 140. For the sake of example, aperture 320 a is shownto have a different shape (elliptical) than a shape of aperture 120 a(rectangular). Other aperture shapes are possible.

As shown, system 300 also includes waveguide 350 (e.g., opticalwaveguide, etc.). To that end, waveguide 350 can be formed from a glasssubstrate (e.g., glass plate, etc.), a photoresist material (e.g., SU-8,etc.), or any other material at least partially transparent to one ormore wavelengths of emitted light 304.

As shown, system 300 also includes an input mirror 360 and an outputmirror 370. Mirrors 360, 370 may be formed from any reflective materialthat has reflectivity characteristics suitable for reflecting (at leastpartially) wavelengths of light 304. To that end, a non-exhaustive listof example reflective materials includes gold, aluminum, other metal ormetal oxide, synthetic polymers, hybrid pigments (e.g., fibrous claysand dyes, etc.), among other examples.

In the example shown, waveguide 350 is positioned between opaquematerial 320 and array 310. However, in other examples, opaque material320 can be instead positioned between waveguide 350 and array 310.

As shown, waveguide 350 may be arranged such that a portion of waveguide350 extends into a propagation path of focused light 302, and anotherportion of waveguide 350 extends outside the propagation path of focusedlight 302. As a result, a first portion of focused light 302 may beprojected onto waveguide 350 (as illustrated by the shaded region on thesurface of waveguide 350).

FIG. 3B illustrates a cross-section view of system 300. As best shown inFIG. 3B, a second portion of focused light 302 may propagate from lens330 to array 310 without propagating through waveguide 350.

In some instances, at least part of the first portion of focused light302 (projected onto waveguide 350) may propagate through transparentregions of waveguide 350 (e.g., from side 350 c to side 350 d and thenout of waveguide 350 toward array 310, without being intercepted bymirror 370. However, in some instances, the first portion of focusedlight 302 may be at least partially intercepted by mirror 370 and thenreflected away from array 310 (e.g., guided inside waveguide 350, etc.).

To mitigate this, in some examples, mirror 370 can be configured to havea small size relative to aperture 320 a and/or relative to a projectionarea of focused light 302 at the location of mirror 370. In theseexamples, a larger portion of focused light 302 may propagate adjacentto mirror 370 (and/or waveguide 350) to continue propagating towardarray 310.

Alternatively or additionally, in some examples, mirror 370 can beformed from a partially or selectively reflective material (e.g., halfmirror, dichroic mirror, polarizing beam splitter, etc.) that transmitsat least a portion of focused light 302 incident thereon through mirror370 for propagation toward array 310. Thus, in these examples as well, alarger amount of focused light 302 may eventually reach array 310.

In some examples, input mirror 360 may be configured to direct emittedlight 304 (intercepted by mirror 360 from emitter 340) into waveguide350. Waveguide 350 then guides light 304 inside waveguide 350 towardoutput mirror 370. Output mirror 370 may then reflect guided light 304out of waveguide 350 and toward aperture 320 a.

As best shown in FIG. 3B for example, input mirror 360 may be tilted atan offset angle 361 toward side 350 c of waveguide 350. For example, anangle between mirror 360 and side 350 c may be less than an anglebetween mirror 360 and side 360 d. In one implementation, offset ortilting angle 361 of mirror 360 is 45°. However, other angles arepossible. In the embodiment shown, input mirror 360 is disposed on side350 a of waveguide 350. Thus, in this embodiment, emitted light 304 maypropagate into waveguide 350 through side 350 c and then out of side 350a toward mirror 360. Mirror 360 may then reflect light 304 back intowaveguide 350 through side 350 a at a suitable angle of entry so thatwaveguide 350 can then guide light 304 toward side 350 b. For example,waveguide 350 can be formed such that angle 361 between sides 350 a and350 c is less than the angle between side 350 a and side 350 d (i.e.,side 350 a tilted toward side 350 c). Input mirror 360 can then bedeposited onto side 350 a (e.g., via chemical vapor deposition,sputtering, mechanical coupling, or another process). However, in otherembodiments, mirror 360 can be alternatively disposed inside waveguide350 (e.g., between sides 350 a and 350 b), or may be physicallyseparated from waveguide 350.

As best shown in FIG. 3B, output mirror 370 may also be tilted towardside 350 c of waveguide 350. For example, an angle 371 between mirror370 and side 350 c may be less than an angle between mirror 370 and side360 d. In one implementation, offset or tilting angle 371 of mirror 370is 45°. However, other angles are possible. Thus, in some examples,input mirror 360 may be tilted in a first direction (e.g., clockwise inthe view of FIG. 3B) toward side 350 c, and output mirror 370 may betilted in a second direction (e.g., opposite to the first direction)toward side 350 c. Output mirror 370 can be physically implemented invarious ways similarly to mirror 360 (e.g., disposed on tilted side 350b of waveguide 350, etc.).

In some examples, waveguide 350 may be formed from a material that has adifferent index of refraction than that of materials surroundingwaveguide 350. Thus, waveguide 350 may guide at least a portion of lightpropagating inside the waveguide via internal reflection (e.g., totalinternal reflection, frustrated total internal reflection, etc.) at oneor more edges, sides, walls, etc., of waveguide 350. For instance, asshown in FIG. 3B, waveguide 350 may guide emitted light 304 (receivedfrom emitter 340) toward side 350 b via internal reflection at sides 350c, 350 d, and/or other sides of waveguide 350.

In the arrangement shown in FIG. 3B for instance, waveguide 350 mayextend vertically (e.g., lengthwise) between sides 350 a and 350 b. Insome examples, side 350 c may correspond to an interface between arelatively high index of refraction medium (e.g., photoresist, epoxy,etc.) of waveguide 350 and a relatively lower index of refraction medium(e.g., air, vacuum, optical adhesive, glass, etc.) adjacent to side 350c. Thus, for instance, if guided light 304 propagates to side 350 c atless than the critical angle (e.g., which may be based on a ratio ofindexes of refractions of the adjacent materials at side 350 c, etc.),then the guided light incident on side 350 c (or a portion thereof) maybe reflected back into waveguide 350. Similarly, guided light incidenton side 350 d at less than the critical angle may also be reflected backinto waveguide 350. Thus, waveguide 350 may control divergence of guidedlight via internal reflection at sides 350 c and 350 d, for example.Similarly, waveguide 350 may extend through the page in the illustrationof FIG. 3B between two opposite sides of waveguide 350 to controldivergence of guided light 304. In some implementations, to facilitatecontrolling the divergence of light 304, sides 350 c may be configuredto be substantially parallel to side 350 d.

Through this process, at least a portion of emitted light 304 (reflectedby input mirror 360 into waveguide 350) may reach tilted side 350 b.Output mirror 370 (e.g., disposed on side 350 b) may then reflect the atleast portion of guided light 304 toward side 350 c and out of waveguide350. For example, offset or tilting angle 361 can be selected such thatreflected light 304 from input mirror 360 propagates into waveguide 350in a particular direction so that light 304 reaches side 350 c (or 350d) at less than the critical angle. As a result, input light 304 can beguided inside waveguide 350 toward side 350 b by reflecting off sides350 c, 350 d, etc. Similarly, offset or tilting angle 371 of outputmirror 370 can be selected such that light 304 reflected by mirror 370propagates toward a particular region of side 350 c at greater than thecritical angle. As a result, light 304 (reflected by output mirror 370)may be (at least partially) transmitted through side 350 c rather thanreflected (e.g., via total internal reflection etc.) back into waveguide350. Further, mirror 370 can be oriented to reflect guided light 304incident thereon toward aperture 320 a. As shown in FIG. 3B for example,aperture 320 a could be located adjacent to the particular region ofside 350 c, and may thus transmit light 304 toward lens 330. Lens 330may then direct light 304 toward a scene.

Emitted light 304 may then reflect off one or more objects (e.g., object398) in the scene, and return to lens 330 (e.g., as part of light 302from the scene). Lens 330 may then focus light 302 (including thereflections of the emitted light beams) through aperture 320 a andtoward array 310.

With this arrangement, system 300 may emit light 304 from asubstantially same physical location (e.g., aperture 320 a) from whichsystem 300 receives focused light 302 (e.g., aperture 320 a). Becausethe transmit path of emitted light 304 and the receive path of focusedlight 302 are co-aligned (e.g., both paths are from the point-of-view ofaperture 320 a), system 300 may be less susceptible to the effects ofparallax than the arrangement of system 290 and emitter 240 of device200 (which are associated with physically separate lenses 230 and 231).For instance, data from a LIDAR device that includes system 300 could beused to generate a representation of the scene (e.g., point cloud) thatis less susceptible to errors related to parallax.

It is noted that the sizes, positions, orientations, and shapes of thecomponents and features of system 300 shown are not necessarily toscale, but are illustrated as shown only for convenience in description.It is also noted that system 300 may include fewer or more componentsthan those shown, and one or more of the components shown could bearranged differently, physically combined, and/or physically dividedinto separate components.

In a first embodiment, the relative arrangement of array 310, aperture320 a, and waveguide 350 can vary. In a first example, opaque material320 (and thus aperture 320 a) can be alternatively disposed betweenarray 310 and waveguide 350. For instance, waveguide 350 can bepositioned adjacent to an opposite side of opaque material 320, whilestill transmitting emitted light 304 along a path that overlaps thepropagation path of focused light 302 transmitted through aperture 320a. In a second example, array 310 can be alternatively disposed betweenwaveguide 350 and opaque material 320. For instance, array 310 mayinclude an aperture (e.g., cavity, etc.) through which emitted light 304propagates toward aperture 320 a (and lens 330).

In a second embodiment, array 310 can be replaced by a single lightdetector instead of a plurality of light detectors.

In a third embodiment, a distance between waveguide 350 and aperture 320a can vary. In one example, waveguide 350 can be disposed along (e.g.,in contact with, etc.) opaque material 320. For instance, side 350 c maybe substantially coplanar with or proximal to aperture 320 a. However,in other examples (as shown), waveguide 350 can be positioned at adistance (e.g., gap, etc.) from opaque material 320 (and aperture 320a).

In a fourth embodiment, system 300 could optionally include an actuatorthat moves lens 330, opaque material 320, and/or waveguide 350 toachieve a particular optical configuration (e.g., focus configuration,etc.) while scanning the scene. More generally, optical characteristicsof system 300 can be adjusted according to various applications ofsystem 300.

In a fifth embodiment, the position and/or orientation of aperture 320 acan vary. In one example, aperture 320 a can be disposed along the focalplane of lens 330. In another example, aperture 320 a can be disposedparallel to the focal plane of lens 330 but at a different distance tolens 330 than the distance between the focal plane and lens 330. In yetanother example, aperture 320 a can be arranged at an offset orientationrelative to the focal plane of lens 330. For instance, system 300 canrotate (e.g., via an actuator) opaque material 320 (and/or waveguide350) to adjust the entry angle of light 302 and/or 304 into aperture 320a. By doing so, for instance, a controller (e.g., controller 292) canfurther control optical characteristics of system 300 depending onvarious factors such as lens characteristics of lens 330, environment ofsystem 300 (e.g., to reduce noise/interference arriving from aparticular region of the scanned scene, etc.), among other factors.

In a sixth embodiment, waveguide 350 can alternatively have acylindrical shape or any other shape. Additionally, in some examples,waveguide 350 can be implemented as a rigid structure (e.g., slabwaveguide) or as a flexible structure (e.g., optical fiber).

In a seventh embodiment, waveguide 350 may have a curved shape or othertype of shape instead of the vertical rectangular configuration shown inFIGS. 3A and 3B. Thus, in this embodiment, array 310 and emitter 340 canbe physically separated in a variety of ways, and waveguide 350 canguide emitted light 304 to output mirror 370 in any path (notnecessarily a vertical or linear path as shown).

In an eighth embodiment, system 300 may alternatively omit input mirror360. For instance, emitter 340 can be arranged to emit light 304 towardwaveguide 350 at a suitable angle of entry so that it reflects off sides350 c, 350 d, etc., without the presence of input mirror 370.

In a ninth embodiment, waveguide 350 can be alternatively implementedwithout tilting side 350 a. For example, side 350 a can be at a same(e.g., perpendicular, etc.) angle relative to sides 350 c and 350 d.With this arrangement for instance, emitter 340 can emit light 304 intoside 350 a (which might not be obstructed by mirror 360).

In a tenth embodiment, system 300 may include multiple output mirrors(between sides 350 a and 350 b of waveguide 350) instead of the singleoutput mirror 370 shown, multiple apertures instead of the singleaperture 320 a shown, and multiple light detector arrays instead of thesingle array 310 shown. For example, a first output mirror may reflect afirst portion of guided light 304 out of waveguide 350 toward a firstaperture, and a remaining portion of the guided light may continuepropagating inside the waveguide toward a second output mirror. Thesecond output mirror may then reflect a second portion of the guidedlight out of the waveguide toward a second aperture, and so on. Thus, inthis embodiment, system 300 may provide multiple co-alignedtransmit/receive channels using a single waveguide.

In an eleventh embodiment, mirrors 360, 370 can be alternativelyimplemented as one or more optical elements (e.g., lenses, prisms,waveguides, etc.) configured to redirect light 304 emitted from emitter340 into waveguide 350 (and/or toward aperture 320 a). For example,mirror 360 and/or 370 can be implemented as total internal reflection(TIR) mirrors (e.g., prisms, etc.) or another optical element assemblydisposed near sides 350 a, 350 b, etc., to direct light 304 intowaveguide 350 and/or out of waveguide 350 toward aperture 320 a.

In a twelfth embodiment, mirrors 360, 370 can be omitted from system300, and waveguide 350 can instead be configured to perform thefunctions described above for mirrors 360, 370. For example, sides 350 aand 350 b of waveguide 350 can be implemented as TIR mirrors thatreflect light 304 into or out of waveguide 350. For instance, tiltingangle 361 (shown in FIG. 3B) can be selected such that light 304 arrivesfrom emitter 340 at side 350 a at less than the critical angle (e.g.,associated with the refractive indexes of waveguide 350 and itssurrounding medium). Alternatively or additionally, for instance,emitter 340 can be arranged to transmit light 304 toward side 350 a(and/or side 350 d) at less than the critical angle, such that light 350may then be internally reflected inside waveguide 360 toward side 350 b.Similarly, tilting angle 371 can be selected such that the guided lightinside waveguide 350 is reflected by side 350 b toward side 350 c atgreater than the critical angle (e.g., so that light 304 can then exitwaveguide 350 at side 350 c after reflecting off side 350 b). Thus, inthis example, waveguide 350 and mirrors 360, 370 can be implemented as asingle physical structure (e.g., without using reflective materials).

FIG. 4A illustrates a first cross-section view of a system 400 thatincludes multiple waveguides 450, 452, 454, 456, according to exampleembodiments. For purposes of illustration, FIG. 4A shows x-y-z axes,where the z-axis extends through the page. System 400 may be similar tosystems 100, 290, and/or 300, and can be used with device 200 instead ofor in addition to system 290 and transmitter 240. For example, the sideof waveguide 450 along the surface of the page may be similar to side350 c of waveguide 350.

As shown, system 400 includes a plurality of waveguides 450, 452, 454,456, each of which may be similar to waveguide 350; a plurality of inputmirrors 460, 462, 464, 466, each of which may be similar to mirror 360;and a plurality of output mirrors 470, 472, 474, 476, each of which maybe similar to output mirror 370.

FIG. 4B illustrates a second cross-section view of system 400, where thez-axis also extends through the page. As shown in FIG. 4B, system 400also includes an opaque material 420, which may be similar to opaquematerial 320 of system 300; and a transmitter 440 that includes one ormore light sources similar to light source 340.

Transmitter 440 may be configured to emit light (in the direction of thez-axis) toward waveguides 450, 452, 454, 456. As shown in FIG. 4A forexample, emitted light 404 from the transmitter may be projected ontowaveguide 450 at a location (shaded region) that overlaps input mirror460, similarly to, respectively, emitted light 304, waveguide 350, andinput mirror 350. To that end, transmitter 440 may include one or morelight sources (e.g., laser bars, LEDs, diode lasers, etc.).

In a first embodiment, transmitter 440 may comprise a single lightsource that transmits light for all the waveguides 450, 452, 454, and456. For example, system 400 may include one or more optical elements(not shown), such as lens, mirrors, beam splitters, etc., that split anddirect respective portions of the light emitted by the single lightsource toward waveguides 450 (e.g., as light 404), 452, 454, and 456.With this arrangement, for example, a single light source can be used todrive multiple transmit channels of system 400 (e.g., where eachtransmit channel is associated with a location of a corresponding outputmirror).

In a second embodiment, a given light source in transmitter 440 can beused to drive fewer or more than four waveguides. For example,transmitter 440 may include a first light source that emits light 404toward input mirror 460, and a second light source that emits light(e.g., split into three separate light beams, etc.) for receipt at inputmirrors 462, 464, and 466.

In a third embodiment, transmitter 440 may include a separate lightsource for driving each waveguide. For example, a first light source mayemit light 404 toward mirror 460, a second light source may emit lighttoward mirror 462, a third light source may emit light toward mirror464, and a fourth light source may emit light toward mirror 466.

Regardless of the number of light sources in transmitter 440, emittedlight beams from the transmitter may then be guided into separatetransmit paths (associated with the positions of the output mirrors)toward an environment of system 400.

For example, light beam 404 could be transmitted into a given surface ofwaveguide 450 (e.g., similar to side 350 c of waveguide 350, etc.), asillustrated by the shaded region in FIG. 4A. Waveguide 450 may thenguide light 404 toward one or more output mirrors arranged along aguiding direction of waveguide 460. For example, output mirror 470 mayreflect a portion 404 a of guided light 404 out of the page (e.g., inthe direction of the z-axis), and through the given surface of waveguide450 toward the scene. Thus, light portion 404 a may define a firsttransmit channel (e.g., LIDAR transmit channel, etc.) that is associatedwith the transmit path described above.

Similarly, a second transmit channel of system 400 may be associatedwith a transmit path defined by waveguide 452 and output mirror 472; athird transmit channel associated with a transmit path defined bywaveguide 454 and output mirror 474; and a fourth transmit channel maybe associated with a transmit path defined by waveguide 456 and mirror476. With this arrangement for instance, system 400 may emit a patternof light beams, arranged according to locations of the output mirrors,toward a scene.

In some examples, a single waveguide can be used to define multipletransmit channels of system 400. As shown in FIG. 4A for example,another portion 404 b of light 404 guided inside waveguide 450 may betransmitted out of waveguide 450 at a different location (shaded region)than the location from which portion 404 a is transmitted out ofwaveguide 450. For instance, system 400 may include another tiltedoutput mirror (not shown) that reflects light portion 404 b out ofwaveguide 450 at the position shown in FIG. 4A. A remaining portion 404a of the guided light 404 may then continue propagating toward mirror470 and then reflect out of waveguide 440 in line with the discussionabove.

Returning now to FIG. 4B, opaque material 420 may define a plurality ofapertures, exemplified by apertures 420 a, 420 b, 420 c, 420 d, and 420e, each of which may be similar to aperture 320 a. For example, aperture420 a may be aligned (e.g., adjacent, overlapping, etc.) with outputmirror 470 similarly to, respectively, aperture 320 a and output mirror370. For example, aperture 420 a may overlap output mirror 470 in thedirection of the z-axis to receive light 404 a reflected by outputmirror 470 out of waveguide 450. Similarly, aperture 420 b can bealigned with output mirror 472, aperture 420 c could be aligned withoutput mirror 474, and aperture 420 d could be aligned with an outputmirror 476. Thus, each aperture may be associated with a position of arespective transmit channel.

Additionally, in some examples, light from the scene (e.g., propagatinginto the page in FIG. 4B) may be focused onto opaque material 420,similarly to light 302 that is focused onto opaque material 320. Inthese examples, system 400 may thus provide multiple receive channelsassociated with respective portions of the focused light projected onopaque material 420 at the respective positions of apertures 420 a, 420b, 420 c, 420 d, etc.

For example, a first portion of the focused light transmitted throughaperture 420 a could be intercepted by a first light detector associatedwith a first receive channel, a second portion of the focused lighttransmitted through aperture 420 b could be intercepted by a secondlight detector associated with a second receive channel, a third portionof the focused light transmitted through aperture 420 c could beintercepted by a third light detector associated with a third receivechannel, and a fourth portion of the focused light transmitted throughaperture 420 d could be intercepted by a fourth light detectorassociated with a fourth receive channel.

With this arrangement, each transmit channel may be associated with atransmit path that is spatially co-aligned (through a respectiveaperture) with a receive path associated with a corresponding receivechannel. Thus, system 400 can mitigate the effects of parallax byproviding pairs of co-aligned transmit/receive channels defined by thelocations of apertures 420 a, 420 b, 420 c, 420 d, etc.

FIG. 4C illustrates a third cross section view of system 400, in whichthe z-axis is also pointing out of the page. For example, one or more ofthe components of system 400 shown in FIG. 4B may be positioned above orbelow (e.g., in the direction of the z-axis) one or more of thecomponents shown in FIG. 4A.

As shown in FIG. 4C, system 400 also includes a support structure 480that mounts a plurality of receivers, exemplified by receivers 410, 412,414, 416, and 418. Further, as shown, system 400 also includes one ormore light shields 482.

Each of receivers 410, 412, 414, 416, 418, etc., may include one or morelight detectors. Additionally, each receiver may be arranged tointercept focused light transmitted through a respective aperture ofopaque material 420 (shown in FIG. 4B). For example, receivers 410, 412,414, 416, 418 may be arranged to intercept focused light that istransmitted, respectively, through apertures 420 a, 420 b, 420 c, 420 d,420 e (shown in FIG. 4B). In one embodiment, receivers 410, 412, 414,416 may be positioned to overlap (e.g., in the direction of the z-axis),respectively, output mirrors 470, 472, 474, 476. In some examples, eachof receivers 410, 412, 414, 416, 418, etc., may include a respectivearray of light detectors connected in parallel to one another (e.g.,SiPM, MPCC, etc.), similarly to the light detectors in any of the arrays110, 210, or 310. In other examples, each receiver may include a singlelight detector.

Accordingly, in some examples, system 400 includes a plurality of lightdetectors (e.g., 410, 412, 414, 416, etc.) that are arranged accordingto an arrangement of a plurality of output mirrors (e.g., 470, 472, 474,476, etc.).

Support Structure 480 may include a solid structure that has materialcharacteristics suitable for supporting receivers 410, 412, 414, 416,418, etc. In one example, support structure 480 may include a printedcircuit board (PCB) to which the light detectors of receivers 410, 412,414, 416, 418, etc., are mounted.

Light shield(s) 482 may comprise one or more light absorbing materials(e.g., black carbon, black chrome, black plastic, etc.) arranged aroundreceivers 410, 412, 414, 416, 418, etc. In some examples, lightshield(s) 482 may prevent (or reduce) light from external sources (e.g.,ambient light, etc.) from reaching receivers 410, 412, 414, 416, 418,etc. Alternatively or additionally, in some examples, light shield(s)482 may prevent or reduce cross-talk between receive channels associatedwith receivers 410, 412, 414, 416. Thus, light shield(s) 482 may beconfigured to optically separate receivers 410, 412, 414, 416, etc.,from one another. In the example shown, light shield(s) 482 may beshaped in a honeycomb structure configuration, where each cell of thehoneycomb structure shields light detectors of a first receiver (e.g.,receiver 410) from light propagating toward light detectors in a secondadjacent receiver (e.g., receiver 412). Other shapes and/or arrangementsof light shield(s) 482 (e.g., rectangular-shaped cells, other shapes ofcells, etc.) are possible.

FIG. 4D illustrates a fourth cross-section view of system 400, where they-axis is pointing through of the page. As shown in FIG. 4D, system 400also includes a lens 430, a light filter 432, a substrate 474, and anoutput mirror 478. As shown in FIG. 4D, waveguide 450 may be at a firstdistance to lens 430, and receivers 410, 418 may be at a second(greater) distance to lens 430.

Lens 430 may be similar to lens 330. For example, lens 430 may focuslight 402 toward opaque material 420 similarly to, respectively, lens330, focused light 302, and opaque material 320. Respective portions offocused light 402 may then be transmitted, respectively, throughapertures 420 a, 420 b, 420 c, 420 d, 420 e, etc. (shown in FIG. 4B). Asshown in FIG. 4D for example, a first portion 402 a of focused light 402may be transmitted through aperture 420 a toward waveguide 450 andreceiver 410. Similarly, a second portion 402 b of focused light 402 maybe transmitted through aperture 420 e toward waveguide 450 and receiver418.

Additionally, as noted above, each aperture may also correspond to aposition from which a transmitted light beam was received by lens 430.Thus, lens 430 may direct each transmitted light beam propagating from aparticular aperture to the same region of the scene from which lens 430focuses received light into that same particular aperture. For example,transmitted light beam 404 a may be directed by lens 430 to a firstregion of the scene according to the location of aperture 420 a. Areflected portion of transmitted light beam 404 a that returns back tolens 430 from the same first region may thus be focused by lens 430 intothe same aperture 420 a (i.e., as part of the first focused lightportion 402 a), for receipt by light detector 410. Similarly, areflected portion of the second transmitted light beam 404 b may befocused by lens 430 toward aperture 420 e and light detector 418 as partof the second focused portion 402 b.

Accordingly, in some embodiments, system 400 may be configured to emit aplurality of transmitted light beams (e.g., 404 a, 404 b) to illuminatea scene. In these embodiments, the plurality of light beams may bespatially arranged based on a physical arrangement of the plurality ofmirrors (e.g., 470, 478, etc.).

Light filter 432 may be similar to light filter 132. For example, lightfilter 432 may include one or more devices configured to attenuatewavelengths of light 402 (e.g., other than wavelengths of emitted light404, etc.). In some examples, filter 432 may extend horizontally(through the page; along the direction of the y-axis) to similarlyattenuate light propagating toward waveguides 462, 464, and 466 (shownin FIG. 4A).

As shown in FIG. 4D, filter 432 may be disposed between the receivers(e.g., 410, 418, etc.) and the waveguides (e.g., 450, etc.) of system400. In another embodiment, filter 432 may be alternatively disposedbetween the waveguides and the lens. In yet another embodiment,substrate 474 can be formed from a material that has the light filteringcharacteristics of filter 432. Thus, in this embodiment, filter 432 andsubstrate 474 may be implemented as a single physical structure. Instill another embodiment, filter 432 can be implemented as multiple(e.g., smaller) filters that are each disposed between lens 430 and arespective one of the receivers. For instance, a first filter can beused to attenuate light propagating toward receiver 410, and a secondseparate filter can be used to attenuate light propagating towardreceiver 418, etc. In one implementation, each one of the multiplefilters can be disposed on a respective one of the receivers. Forinstance, a first filter can be formed on top of receiver 410, a secondfilter can be formed on top of receiver 418, and so on.

Substrate 474 can be formed from an (at least partially) transparentmaterial configured to transmit at least some wavelengths of light(e.g., wavelengths of light 404, etc.) through the substrate. In oneembodiment, substrate 474 may include a glass substrate (e.g., glasswafer). In some examples, substrate 474 may be transparent to visiblelight as well as to the wavelengths of light 404 (e.g., infrared light,etc.).

As shown, waveguide 450 has an input edge 450 a and output edge 450 b,which may be similar, respectively, to sides 350 a and 350 b ofwaveguide 350. As shown in FIG. 4D for example, input edge 450 a may betilted in a first direction (e.g., counterclockwise about the y-axis)toward an output side of waveguide 450 (e.g., the side mounted tosubstrate 474). As such, input mirror 460 can be deposited on the tiltedinput edge 450 a to reflect light 404 (emitted by transmitter 440 towardinput mirror 460) back into waveguide 450 (e.g., toward output mirror470). Further, output edge 450 b may be tilted in a second (opposite)direction (e.g., clockwise about the y-axis) toward the output side ofwaveguide 450. As such, output mirror 470 can be deposited on outputedge 450 b to reflect guided light portion 404 a out of waveguide 450and through aperture 420 a toward lens 430.

As shown in FIG. 4D, waveguide 450 also has another output edge 450 ethat is tilted similarly to edge 450 b toward the output side ofwaveguide 450. As such, output mirror 478 can be disposed on output edge450 e to reflect guided light portion 404 b out of waveguide 450 andtoward aperture 420 e. Thus, in some examples, waveguide 450 may beconfigured to guide emitted light 402 received from an emitter (e.g.,transmitter 44) toward a plurality of output mirrors (470, 478).

To that end, in some examples, waveguide 450 may have a firstcross-sectional size between input edge 450 e and output edge 450 e thatis different (e.g., greater) than a second cross-sectional size ofwaveguide 450 between output edge 450 e and 450 b. Thus, after reachingan output edge (e.g., 450 e) in the guiding direction of waveguide 450(e.g., positive direction on the x-axis), a first portion 404 b of theguided light may be transmitted out of the waveguide as a firsttransmitted light beam (404 b), and a second portion of the guided lightmay continue to propagate (in a smaller-sized section of the waveguide)toward the next output mirror (e.g., 470), that reflects (at leastpartially) the second portion of the guided light out of the waveguideas a second transmitted light beam (404 a).

In some examples, substrate 474 may provide a platform for opticallycoupling (e.g., aligning, etc.) one or more components of system 400.For example, as shown, an output surface of waveguide 450 (e.g., similarto side 350 c of waveguide 350) may be mounted on a first side ofsubstrate 474. Further, as shown, transmitter 440 may be mounted on asecond side of substrate 474 opposite to the first side. Additionally,as shown, opaque material 420 can be mounted on the second side of thesubstrate.

In one example, substrate 474 may be transparent to visible light. Withthis arrangement, in some scenarios, aligning transmitter 440 withmirror 460 can be performed more efficiently (e.g., because mirror 460is viewable through substrate 474, etc.), than if transmitter 440 wasinstead adjacent to edge 450 a of waveguide 450.

In another example, substrate 474 may include alignment marks (e.g.,etched markings or cavities, etc.) on each side of the substrate. Suchalignment marks can be accurately positioned (e.g., using a mask, etc.)during manufacture of substrate 474. In turn, the various componentsmounted to substrate 474 can be more accurately aligned by using suchalignment marks. For example, a robotic tool can be used to depositwaveguides 450, 452, 454, 456, etc., onto the first side of substrate474 can use the alignment marks to accurately deposit the material ofwaveguide 450. Similarly, the alignment marks can be used to moreaccurately place opaque material 420 and transmitter 440 on the secondside of substrate 474.

In one example, opaque material 420 may define a grid of apertures alonga focal plane of lens 430. In some examples, each aperture in opaquematerial 420 may transmit light for a respective transmit/receivechannel associated with a respective portion of the FOV of lens 430 thatis viewable through the respective aperture. In one embodiment, opaquematerial 420 may comprise four rows of 64 apertures, where each row ofhorizontally (e.g., along y-axis) adjacent apertures is separated by avertical offset (e.g., along z-axis) from another row of apertures. Inthis embodiment, system 400 could thus provide 4*64=256 receivechannels, and 256 co-aligned transmit channels. In other embodiments,system 400 may include a different number of transmit/receive channels(and thus a different number of associated apertures).

In one example, system 400 may include 32 waveguides (arranged similarlyto waveguides 450, 452, 454, 456), and each waveguide may guide lightthat is divided into 8 transmitted light beams in a 2×4 grid arrangement(e.g., to drive 8 transmit/receive channels of system 400 that arespatially arranged as two rows of four apertures each). Other examplesare possible.

In some implementations, system 400 can be rotated about an axis whilescanning a surrounding environment using the plurality of co-alignedtransmit/receive channels. Referring back to FIG. 2 for example, system400 can be mounted on a rotating platform, similar to platform 294, thatrotates about an axis (e.g., using actuator 296, etc.) while system 400is transmitting light pulses and detecting reflections thereof (viaapertures 420 a, 420 b, 420 c, 420 d, etc.). In this example, acontroller (e.g., controller 292) or other computer system can receiveLIDAR data collected using the co-aligned transmit/receive channels ofsystem 400, and then process the LIDAR data to generate a 3Drepresentation of the environment of system 400. In one implementation,system 400 can be employed in a vehicle, and the 3D representation maybe used to facilitate various operations of the vehicle (e.g., detectand/or identify objects around the vehicle, facilitate autonomousnavigation of the vehicle in the environment, display the 3Drepresentation to a user of the vehicle via a display, etc.).

It is noted that the various sizes, shapes, and positions (e.g.,distance between adjacent waveguides, etc.) shown in FIGS. 4A-4D for thevarious components of system 400 are not necessarily to scale but areillustrated as shown only for convenience in description. For example,although waveguides 450, 452, 454, 456 are shown in FIG. 4A to extend ina linear direction (e.g., along the direction of the x-axis), one ormore waveguides may alternatively be implemented to extend in a curvedpath or a path having any different type of shape.

In some examples, one or more of the waveguides shown in FIG. 4A mayalternatively extend in a lengthwise direction from an input side to anintermediate location, and then split into multiple branches (e.g.,elongate members, etc.), where each branch includes one or more outputedges and extends in a different direction than other branch(es) of thewaveguide. Other examples are possible.

III. Example Methods

FIG. 5 is a flowchart of a method 500, according to example embodiments.Method 700 presents an embodiment of a method that could be used withsystems 100, 290, 300, 400, and/or device 200, for example. Method 500may include one or more operations, functions, or actions as illustratedby one or more of blocks 502-508. Although the blocks are illustrated ina sequential order, these blocks may in some instances be performed inparallel, and/or in a different order than those described herein. Also,the various blocks may be combined into fewer blocks, divided intoadditional blocks, and/or removed based upon the desired implementation.

In addition, for method 500 and other processes and methods disclosedherein, the flowchart shows functionality and operation of one possibleimplementation of present embodiments. In this regard, each block mayrepresent a module, a segment, a portion of a manufacturing or operationprocess, or a portion of program code, which includes one or moreinstructions executable by a processor for implementing specific logicalfunctions or steps in the process. The program code may be stored on anytype of computer readable medium, for example, such as a storage deviceincluding a disk or hard drive. The computer readable medium may includea non-transitory computer readable medium, for example, such ascomputer-readable media that stores data for short periods of time likeregister memory, processor cache and Random Access Memory (RAM). Thecomputer readable medium may also include non-transitory media, such assecondary or persistent long term storage, like read only memory (ROM),optical or magnetic disks, compact-disc read only memory (CD-ROM), forexample. The computer readable media may also be any other volatile ornon-volatile storage systems. The computer readable medium may beconsidered a computer readable storage medium, for example, or atangible storage device. In addition, for method 500 and other processesand methods disclosed herein, each block in FIG. 5 may representcircuitry that is wired to perform the specific logical functions in theprocess.

At block 502, method 500 involves emitting (e.g., viatransmitter/emitter 440) light (e.g., 404) toward a first end (e.g.,edge 450 a) of a waveguide (e.g., 450). At block 504, method 500involves guiding, inside the waveguide, the emitted light toward asecond end (e.g., edge 450 b) of the waveguide.

At block 506, method 500 involves reflecting (e.g., via output mirror470) a first portion (e.g., 404 a) of the guided light toward an outputsurface (e.g., surface of waveguide 450 mounted on substrate 474, outputside 350 c of waveguide 350, etc.) of the waveguide. In some examples,the first light portion (e.g., 404 a) may be transmitted toward a sceneas a first transmitted light beam. For example, light portion 404 a maybe directed by lens 430 toward the scene as the first transmitted lightbeam.

At block 508, method 500 involves reflecting (e.g., via output mirror478) a second portion (e.g., 404 b) of the guided light toward theoutput surface of the waveguide as a second transmitted light beam.Referring back to FIG. 4D for example, lens 430 may receive the firstlight portion 404 a from a first position of aperture 420 a, and thesecond light portion 404 b from a second position of aperture 420 e. Inturn, lens 430 may transmit the first light beam 404 a toward a firstregion of the scene, and may transmit the second light beam 404 b towarda second region of the scene.

IV. Conclusion

The above detailed description describes various features and functionsof the disclosed systems, devices, and methods with reference to theaccompanying figures. While various aspects and embodiments have beendisclosed herein, other aspects and embodiments will be apparent. Thevarious aspects and embodiments disclosed herein are for purposes ofillustration only and are not intended to be limiting, with the truescope being indicated by the following claims.

What is claimed:
 1. A system comprising: a light emitter configured toemit light; a waveguide optically coupled to the light emitter, whereinthe waveguide is configured to receive light emitted by the lightemitter and to guide the received light within the waveguide; aplurality of mirrors including at least a first mirror and a secondmirror, wherein the first and second mirrors are optically coupled tothe waveguide such that the first mirror reflects a first portion of thelight guided within the waveguide to provide a first transmitted lightbeam and the second mirror reflects a second portion of the light guidedwithin the waveguide to provide a second transmitted light beam; and alens configured to direct the first and second transmitted light beamstoward a scene.
 2. The system of claim 1, further comprising: aplurality of light detectors configured to receive light from the scene.3. The system of claim 2, wherein the lens is further configured tofocus the light from the scene toward the plurality of light detectors,wherein a first focused portion of the focused light includes areflected portion of the first transmitted light beam, wherein a secondfocused portion of the focused light includes a reflected portion of thesecond transmitted light beam, wherein the lens focuses the firstfocused portion toward a first light detector of the plurality of lightdetectors, and wherein the lens focuses the second focused portiontoward a second light detector of the plurality of light detectors. 4.The system of claim 1, further comprising: an opaque material thatdefines a plurality of apertures including at least a first aperture anda second aperture, wherein the first aperture is optically coupled tothe first mirror such that the first transmitted light beam istransmitted through the first aperture, and wherein the second apertureis optically coupled to the second mirror such that the secondtransmitted light beam is transmitted through the second aperture. 5.The system of claim 4, wherein the opaque material is positioned betweenthe waveguide and the lens.
 6. The system of claim 4, furthercomprising: a plurality of light detectors including at least a firstlight detector and a second light detector, wherein the first lightdetector is optically coupled to the first aperture, and wherein thesecond light detector is optically coupled to the second aperture. 7.The system of claim 1, further comprising: an input mirror, wherein theinput mirror is configured to reflect light from the light emitter intothe waveguide.
 8. The system of claim 1, wherein the waveguide is afirst waveguide, further comprising a second waveguide optically coupledto the light emitter, wherein the second waveguide is configured toreceive light emitted by the light emitter and to guide the receivedlight within the second waveguide.
 9. The system of claim 8, wherein theplurality of mirrors further includes a third mirror, wherein the thirdmirror is optically coupled to the second waveguide such that the thirdmirror reflects at least a portion of the light guided within the secondwaveguide to provide a third transmitted light beam.
 10. The system ofclaim 1, further comprising: a transparent substrate, wherein thewaveguide is mounted to the transparent substrate.
 11. The system ofclaim 10, wherein the waveguide is optically coupled to the lightemitter via the transparent substrate.
 12. A light detection and ranging(LIDAR) device comprising: a light emitter configured to emit light; awaveguide optically coupled to the light emitter, wherein the waveguideis configured to receive light emitted by the light emitter and to guidethe received light within the waveguide; a plurality of mirrorsincluding at least a first mirror and a second mirror, wherein the firstand second mirrors are optically coupled to the waveguide such that thefirst mirror reflects a first portion of the light guided within thewaveguide to provide a first transmitted light beam and the secondmirror reflects a second portion of the light guided within thewaveguide to provide a second transmitted light beam; a lens configuredto direct the first and second transmitted light beams toward a scene;and a plurality of light detectors configured to receive light from thescene.
 13. The LIDAR device of claim 12, wherein the lens is furtherconfigured to focus the light from the scene toward the plurality oflight detectors, wherein a first focused portion of the focused lightincludes a reflected portion of the first transmitted light beam,wherein a second focused portion of the focused light includes areflected portion of the second transmitted light beam, wherein the lensfocuses the first focused portion toward a first light detector of theplurality of light detectors, and wherein the lens focuses the secondfocused portion toward a second light detector of the plurality of lightdetectors.
 14. The LIDAR device of claim 13, further comprising: anopaque material that defines a plurality of apertures including at leasta first aperture and a second aperture, wherein the first aperture isoptically coupled to the first mirror such that the first transmittedlight beam is transmitted through the first aperture, and wherein thesecond aperture is optically coupled to the second mirror such that thesecond transmitted light beam is transmitted through the secondaperture.
 15. The LIDAR device of claim 14, wherein the first lightdetector is optically coupled to the first aperture, and wherein thesecond light detector is optically coupled to the second aperture. 16.The LIDAR device of claim 14, wherein the waveguide is disposed betweenthe opaque material and the plurality of light detectors.
 17. The LIDARdevice of claim 12, further comprising: an input mirror, wherein theinput mirror is configured to reflect light from the light emitter intothe waveguide.
 18. The LIDAR device of claim 12, wherein the waveguideis a first waveguide, further comprising a second waveguide opticallycoupled to the light emitter, wherein the second waveguide is configuredto receive light emitted by the light emitter and to guide the receivedlight within the second waveguide.
 19. The LIDAR device of claim 18,wherein the plurality of mirrors further includes a third mirror,wherein the third mirror is optically coupled to the second waveguidesuch that the third mirror reflects at least a portion of the lightguided within the second waveguide to provide a third transmitted lightbeam.
 20. The LIDAR device of claim 12, further comprising: atransparent substrate, wherein the waveguide is mounted to thetransparent substrate.